Method for reworking and cleaning wells

ABSTRACT

A method for reworking and cleaning a well which comprises the steps of setting a packer in the well bore above the formation surrounding the well bore to be treated, inserting tubing through the packer, pumping a mixture of calcium carbide in a liquid hydrocarbon carrier into the area of the well bore to be treated, pumping a hydrocarbon through the tubing to force all of the calcium carbide and liquid hydrocarbon carrier into the area to be treated, pumping an aqueous solution of hydrochloric acid through the tubing, packer and into the well bore and surrounding formation, pumping a liquid hydrocarbon into the tubing to force the calcium carbide, the hydrocarbons and the hydrochloric acid into the formation to be treated, and securing the well bore to prevent escape of the reactants, is disclosed.

United States Patent 1 [111 3,712,380 Caffey [451 Jan. 23, 1973 [54]METHOD FOR REWORKING AND 57 ABSTRACT CLEANING WELLS A method forreworking and cleaning a well Whlch [76] Invent: Caffey, BOX Hermescomprises the steps of setting a packer in the well bore y Ok1a'73742above the formation surrounding the well bore to be [22] Filed: No 30,1970 treated, inserting tubing through the packer, pumping a mixture ofcalcium carbide in a liquid hydrocarbon pp 93,859 carrier into the areaof the well bore to be treated, pumping a hydrocarbon through the tubingto force all 52 us. c1 "166/300, 166/307 the calcium carbide and liquidhydrocarbm carrier 51 Int. Cl. ..E24b 43/25 the area be treated Pumpingaquews [58] Field of Search 166/300 305, 307 270 271 tion ofhydrochloric acid through the tubing, packer 166/272. 252/855C and intothe well bore and surrounding formation, pumping a liquid hydrocarboninto the tubing to force [56] References Cited the calcium carbide, thehydrocarbons and the hydrochloric acid into the formation to be treated,UNITED STATES PATENTS and securing the well bore to prevent escape ofthe reactants, is disclosed. 2,943,681 7/1960 Barrett ..l66/300 71,806,499 5/1931 Ranney ..l66/30O 6 Claims, No Drawings- PrimaryExaminer-Robert L. Wolfe Aztorney-Robert G. McMorrow M... a I" METHODFOR REWORKING AND CLEANING WELLS BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention relates to the reworking of oil and gaswells. More particularly, this invention relates to an improved processfor the reworking of oil, gas, salt water disposal and water floodinjection wells.

2. Description of the Prior Art It is known that in certain instances itis necessary to apply pressure or to use displacement techniques in therecovery of oil and gas from wells. Generally, in order to tap a sourceof oil or gas, it is necessary to not only fracture the stratasurrounding the source to provide access of the oil or gas to the wellbore for recovery, but also it is sometimes necessary to displace theoil or gas by pumping liquids such as water or salt water into thesurrounding strata to displace the oil or gas.

Various methods are known for fracturing the surrounding strata and fordisplacing the oil or gas. Wells can be fractured utilizing bothmechanical and chemical-mechanical means, e.g., using the pressure of aliquid forced into the strata around a well bore to fracture the stratasurrounding the well bore or by chemically generating a pressure using areaction in which a gas is liberated in a confined space, which willgenerate a forcible pressure, and utilizing this pressure alone or incombination with an applied mechanical pressure, as for example,hydraulically, to fracture the surrounding strata. One such method isknown and involves the in situ generation of acetylene by the reactionof calcium carbide and water to produce the pressure needed forfracturing. However, this method has the disadvantage that the reactionproducts, calcium carbonate, results in the formation of lime depositswhich can plug and impede the flow of oil even where the strata has beenfractured to increase the accessibility to the oil and gas reserves.

Methods are also known whereby oil or gas reserves must be displacedforcibly in order to force the oil or gas reserves to the surface. Suchmethods involve the displacement of the oil and gas by pumping water orsalt water into the area, thus forcing the oil or gas to the surface dueto the pressure of the water or salt water used as a displacementliquid. Due to the incompatability of water and oil, emulsions can beformed which thereby impede the flow of the oil.

As a result of the necessity for using displacing means to tap certainoil or gas sources, or the need to fracture the surrounding strata toobtain access to the oil or gas sources, one necessarily must introduceforeign materials into the oil well bore and oil bearing strata toaccomplish these ends. This results in the creation of residues in theoil bearing strata, the formation of oil-water emulsions which aredifficult to break, or the plugging of the strata or the oil boreitself. These problems may not only reduce the yield of the well, butalso could render the well completely unproductive due to plugging,reduced flow and the like.

Accordingly, it is an object of this invention to provide a process forthe reworking of oil and gas wells, and in particular those requiringfracturing, salt water disposal and water flood injection techniqueswherein the above-described problems are minimized and eliminated.

It is also an object of this invention to provide a process whereby anyoil residues can be liquifled, oilwater emulsions can be broken, andsolids can be removed to increase the efficiency and productivity of oiland gas wells.

Additionally, it is an object of this invention to provide a methodwhereby the well can not only be fractured, increasing the access to oilin the surrounding strata, but also whereby the channels previouslycreated in the strata surrounding the well bore can be cleaned as wellas to render removable any solids, residues or difficult to handleliquids present in the strata fractures or well bores.

SUMMARY OF THE INVENTION The objects of this invention are accomplishedaccording to the method described herein. The method of this inventionis a method for reworking a well and comprises the steps of l. setting apacker in the bore of a well above the perforations of the formationsurrounding said well bore to be treated;

. inserting tubing through said packer;

3. pumping a mixture of calcium carbide and a liquid hydrocarbon carrierthrough said tubing and said packer into said well bore and saidformation surrounding said well bore;

. pumping a hydrocarbon through said tubing to force all of said mixtureof calcium carbide and a liquid hydrocarbon carrier into said well boreand surrounding formation;

5. pumping an aqueous solution of hydrochloric acid through said tubingand said packer and into said well bore and surrounding formation;

. pumping a liquid hydrocarbon into said tubing to force said calciumcarbide, said hydrocarbons and said hydrochloric acid into saidformation surrounding said well bore; and

7. securing said well bore to prevent escape of said reactants duringsaid reaction.

DETAILED DESCRIPTION OF THE INVENTION The process of this inventioncontemplates the use of a chemical reaction to generate heat in the wellbore and in the formation surrounding the well bore by the chemicalreaction of reactants injected into the well. By the injection ofcalcium carbide and an aqueous solution of hydrochloric acid, removal ofany corrosion, solid or waxy paraffins and hydrocarbons, and oil wateremulsions, which may restrict the natural flow of previously fracturedoil and gas formations, results. In addition, after the use of themethod of this invention, the pressure needed to inject fluids into saltwater and water flood injection wells is reduced, thereby not onlyincreasing the productivity of said well, but in addition, making thesetypes of well more economical to operate.

In the first step of the process of this invention, a packer or a plugis placed in the bore of a well at an area in the well bore above theformation of the well bore to be treated. Generally, the strata to betreated surrounding the well bore will have been previously fractured,as for example, using conventional means such as liquids under pressureand the like. This packer is set approximately 50 to feet, preferablyfrom about 30 to 60 feet, above the fractured perforations of theformation or strata to be treated to close off the well bore so that thechemical reaction described hereinafter is confined and localized inthat area of the well bore and the surrounding perforations which are tobe treated. Suitable packers are well known in the art, and thosegenerally used in the fracturing of a well are suitable. Where it isdesired to localize the treatment area further, packers can be set inthe well bore both above and below the area to be treated.

Once the packer has been set in the well bore, a tubing is insertedthrough the packer for use in pumping of the materials utilized in thelater steps of the process into the area to be treated. Where twopackers are used, the tubing is inserted into the upper packer. Thetubing runs from the packer to the surface of the well and possessesmeans for completely closing off the area such that once all of thereactants are introduced into the area of the well bore to be treated,they are not forced out through the packer and the tubing to thesurface, but rather are confined in the localized area below the packer.

Once the tubing has been inserted into the packer, a mixture of calciumcarbide and a liquid hydrocarbon carrier is pumped through the tubingand the packer into the well bore to be treated and into the surroundingformation. Suitable hydrocarbons which can be used in this step of theprocess of the invention are materials such as gelled kerosene, lightnaphthas, gasoline, crude and refined oil having an A.P.l. gravity offrom 12 to 25. The gelling of kerosene, naphthas, gasoline and crude isdone with caustic and soaps as is well known in the art. All that isnecessary for the liquid hydrocarbon carrier is that it be inert to thecalcium carbide and substantially free of water which might cause apremature reaction of the calcium carbide. The calcium carbide particlesare dispersed in the liquid hydrocarbon carrier and subsequently pumpedthrough the tubing and packer and into the area to be treated. The sizeof the calcium carbide particles which are used is not a criticalconsideration, however, it is desired that the size be such that mixing,pumping and dispersion is facilitated, settling is minimized, and asurface area is provided which, on contact with the hydrochloric acidand water forced into the well area in a later step of the process ofthis invention, can react smoothly and rapidly to cause the generationof the temperatures desired for the reworking of the well and theformation surrounding the well bore. The size of the calcium carbidegenerally used will generally range from 8 mesh to a 40 mesh, preferablyfrom to 40 mesh, although as indicated above, the size of the calciumcarbide particles used is not a critical consideration. However, use ofa particle size larger than 8 can result in handling and pumpingdifficulties and with a particle size smaller than 40 does not result inany advantages in its use.

In this step of the process of the invention, the calcium carbide willgenerally be used in the ratio of from 3 to 16 percent by weight to theliquid hydrocarbon carrier. The weight ratio of the calcium carbide tothe hydrocarbon carrier ranges from one-half pound per gallon to 1 poundper gallon. Generally, a suitable amount of the hydrocarboncarrier/calcium carbide mixture to be used ranges from 1 gallon to 2gallons per pound of the hydrochloric acid described hereinafter. It isto be recognized that the amount used will depend upon the extent of thefracturing, the porosity of the surrounding rock strata and the like.

In the next step of the process of this invention, a hydrocarbon such aslease crude or distillate is pumped through the tubing and the packer toforce all of the mixture of the calcium carbide and the liquidhydrocarbon carrier into the well bore and the surrounding formation.This not only accomplishes the displacement of the calcium carbide intothe area of the well to be treated, but minimizes any reaction ofcalcium carbide and the aqueous hydrochloric acid solution injected inthe later step of the process of this invention from generating heat andpressure due to the reaction of the calcium carbide and the aqueoushydrochloric acid solution in the tubing area. Not only does this giverise to a more efficient use of the process of this invention butminimizes any difficulties which might be encountered by the in situgeneration in the tubing of the heat and pressure due to the reaction ofthe calcium carbide and the aqueous solution of the hydrochloric acid.In addition, the forcing of the hydrocarbon through the tubing todisplace the mixture of the calcium carbide and the liquid hydrocarboncarrier used in a previous step not only minimizes any difficultieswhich might arise as a result of the in situ generation in the tubingbut in addition provides for the displacement further of the liquidhydrocarbon and calcium carbide into the surrounding rock strata to becleaned and reworked.

In the next step of the process of this invention, an aqueous solutionof hydrochloric acid is pumped through the tubing and the packer intothe well bore and surrounding formation in order to contact the aqueoussolution of the hydrochloric acid with the calcium carbide previouslypumped into the well bore and the surrounding formation. In this step ofthe process of this invention, the second reactant, the aqueous solutionof the hydrochloric acid, is forced into the area below the packer andinto contact with the first reactant, the calcium carbide, resulting inthe reaction of the calcium carbide and the water contained in theaqueous solution. Heat is generated due to the reaction of the calciumcarbide and the water forming acetylene gas. The amount of the aqueoussolution of the hydrochloric acid will be dependent upon the amount ofthe calcium carbide used, but generally will range from 1 gallon of acidto 1.5 gallons of acid for each pound of calcium carbide used. Use ofless than 1 gallon of acid or greater than 2 gallons of acid generallyreduces the efficiency of the process either due to incomplete reactionor the larger volumes of acid which must be pumped into the area to betreated. it is generally desired that an excess of the aqueous solutionof hydrochloric acid be used in order to insure that all of the calciumcarbide has reacted, resulting in a more efficient operation of theprocess of this invention. Generally, the concentration of thehydrochloric acid used will range from 1 to about 28 percent by weight.Although a concentration of from 1 to about 28 percent hydrochloric acidgenerally is used in this step of the process of this invention, theamount of the acid used will be determined not only by the amount ofcalcium carbide used, but also by the characteristics of the formationand the condition of the well to be treated.

For example, such factors as limestone, sandstone, and solubilities ofeach may determine that a greater or lesser amount of the hydrochloricacid solution be used. More acid will be required in limestoneformations due to the solubility of the formation itself. Generally, anamount of from 1 to L5 barrels of the aqueous solution of thehydrochloric acid ranging from 1 to 28 percent by weight can be used foreach barrel of the calcium carbide liquid hydrocarbon mixture previouslypumped into the well bore and surrounding formation and is suitable. Useof less than a 1 percent solution of the hydrochloric acid generallydoes not provide sufficient acid to dissolve the calcium carbonateformed as a reaction product and use of a concentration greater than 28percent generally does not provide any additional advantages.

This step of the process of this invention is followed by a pumping of aliquid hydrocarbon into the tubing to force all of the calcium carbide,the hydrocarbons used and the hydrochloric acid solution into the areabelow the packer and into the formation surrounding the well bore suchthat the in situ reaction of the calcium carbide and the water occurs inthe area of the well bore and the rock formation to be treated. Upon themixing of these materials, the calcium carbide reacts with the aqueoushydrochloric acid solution generating temperatures in the formation inexcess of about 475F and simultaneously acetylene is released into theformation due to the reaction. This in situ generation of heat andpressure causes a melting of any paraffins, oil residues and a breakingof any hydrocarbon and water emulsions which might be restricting thenatural flow of the oil through the surrounding formations and the wellbore. Not only does the heat and pressure cause the melting of paraffinresidues, hydrocarbon plugs and the like in the well bore and thesurrounding formation, but the heat and pressure clean the fractures ofthe surrounding formation such that access to the oil and gas reservesin the formation through the fractures is improved and also for thosewells at which liquid displacement is necessary to obtain the oil andgas reserves. The pressures needed to accomplish this displacement aremarkedly reduced due to the cleaning and clearing of not only the wellbore but the fracture surrounding the well bore. The temperaturesgenerated in situ and the gas generated in situ disturb thesurroundings, increasing the flow of the oil or gas molecules in theformation, causing them to move to the fractures into the well bores.Thus, the generation of the heat and pressure not only reduces theamount of work which is necessary to tap the oil reserves, but alsoleads to an increase in productivity of the well due to the disturbingof the surrounding strata restricting the free movement of the oilmolecules in the formation through the fractures to the bore.

The hydrochloric acid used in this step of the process of this inventionnot only increases the rate of reaction between the calcium carbide andthe water, but also neutralizes and dissolves any lime deposits whichwould be left in and on the formation as a result of the reactionproduct formed by the reaction of the calcium carbide and water. Theacid not only dissolves the lime formed as a result of the reaction, butincreases the rate at which the thermal reaction occurs, providing ahigher degree of temperature in the formation and a shorter period oftime for the reworking of the well.

Once the liquid hydrocarbon pumped into the well bore through the tubingand the packer is displaced in the well, the well bore is closed orsecured in such a manner that the escape of the reactants through thepacker and the tubing to the surface is prevented and the reaction ofthe calcium carbide and the aqueous solution of the hydrochloric acid islocalized in the area of the well bore to be treated. This is done notonly as a safety precaution to prevent escape of the reactants due tothe pressure build-up and the high temperatures generated, but also toutilize efficiently the reactants in the area of the well bore andformation to be treated.

Generally once the well bore is secured, the reactants are held in thearea below the packer for a period of time sufficient to allow thegeneration in situ of the temperatures set forth above to maximize thethermal reaction for the reworking of the well bore and the surroundingstrata. Generally, this period of time will range from about 4 to about12 hours.

Once the reaction between the calcium carbide and the aqueoushydrochloric acid solution has run its course, the liquids contained inthe well bore and surrounding strata can be allowed to flow back to thesurface of the well or be pumped back, if necessary, and the well becleaned and swabbed where desired. As indicated above, the temperaturesgenerated in situ liquifies any hydrocarbon residue pluggings, breaksany oil and water emulsions and generally cleans not only the well borebut the surrounding strata increasing the productivity and minimizingthe difficulty in recovering the oil and gas reserves present in thewell area. In addition, by the use of the method of this invention, nolime deposits are created as reaction products which could plug orreduce the productivity.

As indicated above, this invention provides a method for reworking awell in order to increase the productivity of the well, to remove anyforeign materials causing difficulty in attaining access to the oil andgas reserves present therein and results in a well which is easier totap and which can be operated more efficiently.

in order to illustrate the advantages of the process of this inventionfor melting a hydrocarbon residue and to show the advantageous resultsobtained due to the use of hydrochloric acid in preventing lime depositswhich could ultimately reduce the effectiveness of the process, thefollowing examples are provided to illustrate the process of thisinvention without thereby limiting the process of the invention.

EXAMPLES Eight wells have been subjected to the treatment of the processof this invention. Described below is the treatment on two of the wells.These two wells are producing oil and gas wells. The other wells treatedhave responded similarly.

The first well treated was a Mississippi limestone well. it wasstimulated by a large water-frac type treatment, with approximately12,000 barrels of water being used. This is an average size treatmentand is conventionally used in this area. The production of the well ascompleted was barrels of oil per day (BOPD) and 1.2 MM cubic feet perday (CFD). In four years production had declined to 3 BOPD and 35 M CFD.

The well was treated according to the process of this invention usingthe following steps: Tubing and packer were run into the well and thepacker set approximately 35 feet above the perforations of the strata tobe treated. Lease oil was then pumped via tubing to fill the tubing andpump into the formation to ensure the zone would accept the treatment.Next, 800 pounds of calcium carbide and 800 gallons of refined l8gravity oil were mixed in a paddle mixer tank. This resulted in a totalvolume of approximately 1,000 gallons. This mixture was then pumped intothe well via the tubing and without stopping the pump a barrel spacer ofthe lease oil was pumped. The spacer of lease oil prevented the calciumcarbide mixture and the acid subsequently pumped into the well fromreacting in the tubing or well bore. Immediately following the 15 barrellease oil spacer, 1,500 gallons of a 15 percent aqueous hydrochloricacid was pumped into the well via the tubing. The acid was thendisplaced with lease oil down the tubing and out into the zone tocontact the calcium carbide. Surface pumping pressure during theoperation varied from 1,000 psi to 3,000 psi. The well was then shut infor 12 hours. The well was opened the next morning and flowed andswabbed to recover the treatment fluid. All the fluid, acid water andlease oil was recovered in 18 hours and the well was flowing with 100psi on the tubing.

Ninety days after the treatment by the process of this invention, thewell was producing 18 BOPD and 8 BWPD with 180 M CFD. The water wastested and was believed to be the frac water used in the originaltreatment in 1965, since the well was not making any water prior to thetreatment.

The second well treated was a comingled Cromwell (sandstone) and Hunton(limestone) well in southern Oklahoma. The original completion was inthe Hunton zone only and produced after an acid treatment, for 8 years.At that time an acid-frac treatment was done on the Hunton zone, and theCromwell zone was opened and fracture treated with a sand-oil treatment.In 12 years production had declined from over 100 BOPD to 8 BOPD. Thiswell was treated as follows:

Tubing and packer were run and set 50 feet above both zones. Ten feet ofCromwell and 20 feet of Hunton were open. A sufficient volume of leaseoil was pumped via the tubing to ensure the zones would accept thetreatment. 800 pounds of calcium carbide and 800 gallons of refined 20gravity oil were mixed and the one-half of the mixture, approximately500 gallons, was pumped into the well via the tubing and followed with10 barrels of a lease oil spacer. Then 750 gallons of a 15 percentaqueous hydrochloric acid were pumped and displaced clear of the packer.Forty /a inch rubber ballsealers in lease oil were injected and pumpedvia the tubing to plug off the perforations of one of the zones. Theabove steps were repeated to treat one-half the treatment in each of theopen zones. The surface pumping pressures on the first zone wereapproximately 750 psi and on the second zone the pressure was 850 psi.The pressure differences indicated two different zones were treated.After the treatment fluids were swabbed back, the well was put intoproduction and has been averaging 40 BOPD.

What is claimed is:

1. A method for reworking and cleaning a previously fractured andacidized well comprising the steps of 1. setting a packer in the bore ofa well above the perforation of the formations surrounding said wellbore to be treated;

2. inserting tubing through said packer;

3. pumping a mixture of calcium carbide and a liquid hydrocarbon carrierwhich is inert to the calcium carbide and free of water through saidtubing and said packer into said well bore and said formation, whereinthe weight ratio of the calcium carbide to the liquid hydrocarboncarrier ranges from onehalf pound per gallon to 1 pound per gallon;

4. pumping a hydrocarbon through said tubing to force all of saidmixture of calcium carbide and the liquid hydrocarbon carrier into saidwell bore and surround formation;

5. pumping an aqueous solution of hydrochloric acid through said tubingand said packer and into said well bore and surrounding formation;

6. pumping a liquid hydrocarbon into said tubing to force said calciumcarbide, said hydrocarbons and said aqueous solution of hydrochloricacid into said formation surrounding said well bore, said calciumcarbide and said aqueous solution of hydrochloric acid then being inreactive contact, wherein the concentration of the aqueous solution ofhydrochloric acid ranges from 1 to 28 percent by weight, and wherein thevolume ratio of the aqueous solution of hydrochloric acid to the calciumcarbide ranges from 1 to 2 gallons per pound; and

7. securing said tubing to prevent escape of said reactants, the calciumcarbide and water reacting exothermally to yield gaseous acetylene andlime, the exothermic heat of reacting melting any paraffins and oilresidues present and the pressure of the gaseous acetylene breaking anyhydrocarbon and water emulsions present and cleaning the formation, thehydrochloric acid accelerating the calcium carbide-water reactions andin situ reacting with the lime to thereby avoid lime deposits in theformation.

2. A method for reworking and cleaning a previously fractured andacidized well comprising the steps of 1. setting packers in a well boreabove and below the perforations of the formations surrounding said wellbore to be treated;

2. inserting tubing through the upper packer;

3. pumping a mixture of calcium carbide and a liquid hydrocarbon carrierwhich is inert to the calcium carbide and free of water through saidtubing and said upper packer into said well bore and said formation,wherein the weight ratio of the calcium carbide to the liquidhydrocarbon carrier ranges from one-half pound per gallon to 1 pound pergalion;

4. pumping a hydrocarbon through said tubing to force all of saidmixture of calcium carbide and a liquid hydrocarbon carrier into saidwell bore and surrounding formations;

5. pumping an aqueous solution of hydrochloric acid through said tubingand said upper packer and into said well bore and surrounding formation;

6. pumping a liquid hydrocarbon into said tubing to force said calciumcarbide, said hydrocarbons and said aqueous solution of hydrochloricacid into said formations surrounding said well bore, said calciumcarbide and said aqueous solution of hydrochloric acid then being inreactive contact, wherein the concentration of the aqueous solution ofhydrochloric acid ranges from 1 to 28 percent selected from the groupconsisting of gelled kerosene,

by weight, and wherein the volume rat o f th light naphthas, gasoline,and crude and refined oil havaqueous solution of hydrochloric acid tothe calciing an A.P.l. gravity of from 12 to 25.

m Carbide ranges from 1 l 2 gallons P P 4. The method of claim 2 wherethe hydrocarbon is and 5 selected from the group consisting of gelledkerosene, Securing Said tPbing to Prevent escape of i reac' lightnaphthas, gasoline, and crude and refined oil havtants, the calcnimcarbide and water reacting exing an ARI. gravity Offmm 12 to 25.

othermally to yield gaseous acetylene and lime, the The process ofclaim1 further comprising exothermic heat of reacting melting any paraffinsand oil residues present and the pressure of the gaseous acetylenebreaking any hydrocarbon and water emulsions present and cleaning theformation, the hydrochloric acid accelerating the calcium carbide-waterreactions and in situ reacting with the lime to thereby avoid limedeposits in the 15 formation.

3. The method of claim 1 where the hydrocarbon is 8. permitting thereaction to proceed for from about 4 to about 12 hours prior toreturning the well to production status.

6. The process of claim 2 further comprising 8. permitting the reactionto proceed for from about 4 to about 12 hours prior to returning thewell to production status.

2. inserting tubing through the upper packer;
 2. A method for reworkingand cleaning a previously fractured and acidized well comprising thesteps of
 2. inserting tubing through said packer;
 3. pumping a mixtureof calcium carbide and a liquid hydrocarbon carrier which is inert tothe calcium carbide and free of water through said tubing and saidpacker into said well bore and said formation, wherein the weight ratioof the calcium carbide to the liquid hydrocarbon carrier ranges fromone-half pound per gallon to 1 pound per gallon;
 3. pumping a mixture ofcalcium carbide and a liquid hydrocarbon carrier which is inert to thecalcium carbide and free of water through said tubing and said upperpacker into said well bore and said formation, wherein the weight ratioof the calcium carbide to the liquid hydrocarbon carrier ranges fromone-half pound per gallon to 1 pound per gallon;
 3. The method of claim1 where the hydrocarbon is selected from the group consisting of gelledkerosene, light naphthas, gasoline, and crude and refined oil having anA.P.I. gravity of from 12 to
 25. 4. The method of claim 2 where thehydrocarbon is selected from the group consisting of gelled kerosene,light naphthas, gasoline, and crude and refined oil having an A.P.I.gravity of from 12 to
 25. 4. pumping a hydrocarbon through said tubingto force all of said mixture of calcium carbide and the liquidhydrocarbon carrier into said well bore and surround formation; 4.pumping a hydrocarbon through said tubing to force all of said mixtureof calcium carbide and a liquid hydrocarbon carrier into said well boreand surrounding formations;
 5. pumping An aqueous solution ofhydrochloric acid through said tubing and said upper packer and intosaid well bore and surrounding formation;
 5. pumping an aqueous solutionof hydrochloric acid through said tubing and said packer and into saidwell bore and surrounding formation;
 5. The process of claim 1 furthercomprising
 6. The process of claim 2 further comprising
 6. pumping aliquid hydrocarbon into said tubing to force said calcium carbide, saidhydrocarbons and said aqueous solution of hydrochloric acid into saidformations surrounding said well bore, said calcium carbide and saidaqueous solution of hydrochloric acid then being in reactive contact,wherein the concentration of the aqueous solution of hydrochloric acidranges from 1 to 28 percent by weight, and wherein the volume ratio ofthe aqueous solution of hydrochloric acid to the calcium carbide rangesfrom 1 to 2 gallons per pound; and
 6. pumping a liquid hydrocarbon intosaid tubing to force said calcium carbide, said hydrocarbons and saidaqueous solution of hydrochloric acid into said formation surroundingsaid well bore, said calcium carbide and said aqueous solution ofhydrochloric acid then being in reactive contact, wherein theconcentration of the aqueous solution of hydrochloric acid ranges from 1to 28 percent by weight, and wherein the volume ratio of the aqueoussolution of hydrochloric acid to the calcium carbide ranges from 1 to 2gallons per pound; and
 7. securing said tubing to prevent escape of saidreactants, the calcium carbide and water reacting exothermally to yieldgaseous acetylene and lime, the exothermic heat of reacting melting anyparaffins and oil residues present and the pressure of the gaseousacetylene breaking any hydrocarbon and water emulsions present andcleaning the formation, the hydrochloric acid accelerating the calciumcarbide-water reactions and in situ reacting with the lime to therebyavoid lime deposits in the formation.
 7. securing said tubing to preventescape of said reactants, the calcium carbide and water reactingexothermally to yield gaseous acetylene and lime, the exothermic heat ofreacting melting any paraffins and oil residues present and the pressureof the gaseous acetylene breaking any hydrocarbon and water emulsionspresent and cleaning the formation, the hydrochloric acid acceleratingthe calcium carbide-water reactions and in situ reacting with the limeto thereby avoid lime deposits in the formation.
 8. permitting thereaction to proceed for from about 4 to about 12 hours prior toreturning the well to production status.
 8. permitting the reaction toproceed for from about 4 to about 12 hours prior to returning the wellto production status.